1. Field of the Invention
This invention relates to a new process for the production of compounds containing isocyanurate groups and olefinic double bonds by reacting polyisocyanates containing isocyanurate groups with compounds containing isocyanate-reactive hydrogen atoms and olefinic double bonds, to the reaction products obtainable by this process and to their use as binder or as binder component in coating compositions crosslinkable by high-energy radiation.
2. Description of the Prior Art
Compounds containing olefinically unsaturated groups have long been known as binder-containing coating compositions. They are hardened by high-energy radiation, such as UV-radiation or electron beams, and are used for example for coating heat-sensitive substrates, such as wood or for the production of coatings for graphic purposes, i.e. for example in the printing industry or in the production of printed wiring boards.
A sub-group of radiation-crosslinked coating compositions of the type in question are urethane oligomers modified by compounds containing both ethylenically unsaturated groups and also isocyanate-reactive groups. Oligomers such as these are known, particularly for applications in the printing industry, and are described for example in DE-OS Nos. 21 15 373 and 21 21 253 and in GB-PS No. 1,379,228.
Radiation-crosslinking coating compositions which may be based on different types of oligourethanes have recently been described, again for applications in the printing industry (British Pat. No. 1,491,695).
Among those oligourethanes, a polyisocyanate modified by ethylenically unsaturated groups is particularly remarkable because, in addition to the purpose states in the above-mentioned patent, it is also suitable for the production of high quality lacquers. This particular oligourethane is based on the biuret-group-containing aliphatic polyisocyanate which corresponds to the following idealized formula ##STR1##
Olefinically unsaturated oligourethanes based on this polyisocyanate, i.e. in particular its reaction products with hydroxyalkyl acrylate or methacrylate, may be reacted under the influence of high-energy radiation to form highly crosslinked, hard coatings or, alternatively, are suitable for use as additives to conventional radiation-crosslinking coating compositions to which they impart greater hardness or better abrasion resistance for example. However, their particular advantage lies in the fact that they may be used for producing coatings at room temperature, thereby enabling heat-sensitive substrates, such as wood, paper or leather, to be coated.
However, the oligourethanes referred to are also attended by certain disadvantages. Thus, radiation crosslinking is accompanied by more or less serious discoloration which is particularly troublesome in the coating of white and light-colored substrates. In addition, their weather resistance is often inadequate.
It has now surprisingly been found that these disadvantages may be overcome by using isocyanurate-group-containing polyisocyanates based on aliphatic and/or cycloaliphatic polyisocyanates for the production of olefinically unsaturated isocyanate addition products.
This discovery is particularly surprising in view of the fact that two-component polyurethane lacquers based both on aliphatic polyisocyanates containing biuret groups and on aliphatic polyisocyanates containing isocyanurate groups may be used with equal effect for the production of light-stable and weather-resistant coatings, so that radiation-crosslinkable binders based on isocyanurate polyisocyanates could not be expected to differ with advantage in these properties from radiation-crosslinkable binders based on biuret polyisocyanates.